In the U.S. from 1979 to 2021, the inflation-adjusted average income of households in the top 20% of income rose by 158%. In comparison, the income of the lowest 20% rose by 93%, and the income of the middle 20% rose by 46%. These figures include nearly all sources of income, such as wages, salaries, capital gains, rental income, and government and employer-provided benefits like food stamps and health insurance. Comparisons of income groups over time often do not represent the experiences of specific people because they typically move through life stages in which their income varies significantly, causing them to move in and out of different income groups. Many factors help and hinder income growth, but some of the primary ones are productivity, work hours, government benefits, and regulations.